Photograph of implantable syncope monitor. Arrows point to sensing electrodes.

A subcutaneous pocket was fashioned in the left pectoral region under local anesthesia. The device was placed within the pocket and rotated through 360° to optimize the magnitude of the recorded R-wave electrogram. It was then fastened to the underlying tissue at opposite corners of the device with nonabsorbable sutures. The incision was then closed with absorbable sutures, and a satisfactory electrogram was verified after wound closure. Devices were explanted after a diagnosis was obtained.

Follow-up

All patients were followed in the pacemaker clinic at 1, 2, and 4 weeks after device implantation and subsequently at monthly intervals. Each visit included a patient interview and device interrogation. Patients were seen immediately if they had activated the device.

From September 1992 to September 1994, 209 patients were assessed for syncope. A presumptive diagnosis was obtained in 146 patients after a history, physical examination, ECG, and tilt table test. Forty-one of the remaining patients underwent electrophysiological testing. Sixteen patients with negative electrophysiological testing and unexplained recurrent syncope who were able to return for follow-up and capable of informed consent were approached to participate in the study. All patients approached consented to participate. Before enrollment 15 patients had recurrent syncope (8.7±6.1 episodes, mean±SD) and 1 patient had a single episode of syncope with serious injury in a motor vehicle accident (Table 1
⇓
). The mean age was 57±19 years. There were 12 men. Concomitant heart disease was present in 8 patients; ischemic heart disease in 5, hypertension in 1, cardiac transplantation in 1, and hypertrophic cardiomyopathy in 1. One of the remaining 7 patients had mitral valve prolapse with mild mitral regurgitation on echocardiography. Repeated ambulatory or in-hospital monitoring was negative in all patients. Tilt table testing and electrophysiological studies were negative in all patients. All patients in whom device implantation was attempted had satisfactory ECG sensing, with a mean sensed QRS amplitude of 265±130 μv.

View this table:

Table 1.

Demographic Profile of Patient Population

Spontaneous syncope occurred in 15 of 16 patients (94%), a mean of 4.4±4.2 months after device implantation (range, 6 days to 14 months). The remaining patient has not had syncope and continues to be followed.

Table 2
⇓
summarizes the etiology and treatment of syncope in the 15 patients with recurrence during follow-up. Syncope was secondary to bradyarrhythmia in 7 patients (47%); sinus arrest in 4, complete heart block in 2, and sick sinus syndrome in 1. In this group, the mean baseline corrected sinus node recovery time was 280±105 seconds, and the HV interval was 57±8.1 ms. Syncope was secondary to tachyarrhythmia in 2 patients (17%). Patient 5 had AV node reentrant tachycardia and underwent AV node modification. Repeat electrophysiological study showed only single AV node echo cycles after addition of isoproterenol and atropine. Spontaneous syncope was associated with a narrow complex tachycardia at a rate of 180 beats per minute. The patient underwent repeat AV node modification and has had no further syncopal episodes during 15.5 months of follow-up. Patient 6 had nonsustained ventricular tachycardia at a rate of 240 beats per minute during spontaneous presyncope. No ventricular arrhythmias (including nonsustained ventricular tachycardia) were induced at baseline electrophysiological study.

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